Counter balance



Aug. 25, 1959 R. J STAVA ET AL COUNTER BALANCE 3 Sheets-Sheet 1 Filed Dec. 5, 1954 w W M g Aug. 25, 1959 R. J. STAVA ETAL COUNTER BALANCE 3 Sheets-Sheet 3 Filed Dec. 3, 1954 56 A 60 x I Mm 6/ United States Patent Gfifice 2,96%,202 Patented Aug. 25, 1359 COUNTER BALANCE Robert J. Stava, deceased, late of University Heights, Ohio, by Eleanore Grace Stava, executrix, University Heights, Ohio, and Oswald Conrad Hollstein, Cleveland, Ohio, assignors to Picker X-Ray Corporation, VgagEMfg. Div. Inc., Cleveland, Ohio, a corporation Application December 3, 1954, Serial No. 472,985

6 Claims. (Cl. 248-423) This invention relates generally to a counterbalancing system and more particularly is directed to an improved arrangement for controlling the counterbalancing force throughout its range of operation and in the event of failure.

In many types of apparatus, it is essential that the Weight of an object be counterbalanced against free vertical movement. Conventional counterbalancing systems for such an apparatus are subject to failure which is apt to result in damage or injury to anything in the path of the counterbalanced member. In most applications, the possibility of damage or injury to an object in the path of travel of the counterbalanced member cannot be tolerated and it is desirable to include a control factor which will immobilize the counterbalanced system in the event of a system failure.

An exemplary application where potential injury cannot be tolerated is in the use of X-ray apparatus for rotational therapy in the manner and form shown and described in our co-pending application entitled Rotational Therapy X-ray Method and Apparatus, Serial No. 410,868, filed on February 17, 1954. This apparatus includes an X-ray tube head which is movably supported in a vertical frame for rotation about a patient intersecting the plane of rotation. Vertical movement of the X-ray tube head must be counterbalanced at all times to prevent injury to the patient. In this application, the X-ray tube head is coupled to a spring suspension through the medium of flexible connecting cables and, if one or more of the connecting cables should break, the X-ray tube head assembly would drop upon and injure any patient in the path of its vertical travel. Accordingly, it is a principal object of this invention to provide a mechanism for immobilizing a counterbalanced system in the event of a system failure.

Although a spring suspension may be entirely adequate to counterbalance an object against free vertical movement, the extension of the spring suspension results in .a non-uniformity of the counterbalancing force over the operative range which prevents free effortless movement 'of the counterbalanced object. Therefore, a further object of this invention relates to the improvement of the counterbalancing mechanism to achieve a counterbal- :ancing effect that will be substantially uniform .over the entire range of movement of the counterbalanced object.

Briefly, in accordance with this invention, an operafive member, such as an X-ray tube, is mounted on a frame for movement in a vertical plane. The movable mounting includes an overhead flexible connection between the member and a spring suspension which is anchored to the base of the frame. The flexible connection extends about a free running overhead drum assembly which compensates for the spring extension to maintain a susbtantially uniform counterbalancing effect throughout the range of movement. The connection also includes a latch mechanism arranged for automatic interlocking co-action with the supporting frame in the event of a connection failure, thus immobilizing the system and preventing damage or injury to an object in the path of travel of the counterbalanced member.

In the drawings:

Fig. 1 is a perspective view of a rotational therapy X-ray apparatus with the interior of the vertical frame supports exposed to illustrate the counterbalancing arrangement of this invention;

Fig. 2 is a broken view illustrating portions of the interior of one of the vertical frame supports;

Figs. 3 and 4 are sectional views taken along the lines 3-3 and 4-4- in the spring and cable assembly of Fig. 2 of the drawings;

Fig. 5 is a top view of one end of the vertical frame illustrating the counterbalancing cable drum assembly; and

Fig. 6 is an end view of the cable and drum assembly of Fig. 5;

Fig. 7 is a vertical section taken on a plane indicated by the line 7-7 of Fig. 9;

Figs. 8, 9 and 10 are horizontal sections taken on planes indicated by the lines 83, 9-9 and 10-10 respectively in Fig. 7.

Referring now more particularly to Fig. 1 of the drawings there is shown an exemplary application of the improved counterbalancing system of this invention to a rotational therapy X-ray apparatus wherein an X-ray tube head assembly 10 is pivotally supported within a suitable mounting yoke assembly 12 which is in turn mounted for horizontal movement along vertically spaced rails 13 and 14. These rails are secured at their respective extremities in carriages 15 which are mounted for movement along vertical frame supports 17 and 18 of a suitable overhead frame in a manner and form more particularly described in the above-mentioned copending application.

The arrangement illustrated in Fig. 1 permits the entire tube head assembly 10 including the composite yoke mounting assembly 12 .to be positioned in a vertical plane within the suporting overhead frame. The yoke assembly 12 can be moved horizontally along the horizontal rails 13 and 14 which in turn are movable as a unit with the carriages 15 along the vertical frame supports 17 and 18. An operator can thus direct an X-ray beam at an object of examination or treatment from any direction or angle Within the limited confines of the supporting frame, and it is possible to guide the entire assembly so that the focal spot of the X-ray beam travels in the vertical plane along a circular path with the object of treatment forming the fulcrum of rotation.

It is readily apparent from the drawings that the object of treatment will intersect the vertical plane of rotation of the tube head assembly 19 and therefore lies in the vertical path thereof. Accordingly, the entire tube head assembly 10 is counterbalanced by means of a spring suspension having a plurality of helical coiled springs 20 which are anchored at one end to the base 16 of the vertical overhead frame and are coupled at the other end to flexible wire cables 22 and 23. The cables 22 and 23 are attached to a suitable cable drum 24 which is rotatably mounted on the cross head 19 of the overhead frame. This description will be limited to the counterbalancing mechanism at only one side of the overhead frame, it being understood that such mechanism is duplicated on the other side of the frame.

The flexible cable connection to the tube head assembly 10 is made by connecting the free extremities of cables 26 and 27 to the corresponding rail carriage 15 at each side of the overhead frame; the other extremity of each of these cables being attached to a compensating cam type of drum 25 in a manner to be hereinafter more fully described. The cable connections to the rail carriages 15 are preferably made through the medium of a toggle "h .3 type link 28 to permit uniform distribution of load tension through the connecting cables.

The principal operative elements of the counterbalancing system are shown in greater. detail in 2" through of the drawings. Thus, in Pig. 2 the helical springs 20 which provide the counterbalancing force are shown anchored at their lower extremities to a spring holder bar 29 which in turn is secured to the base 16! of the corresponding vertical frame support. The upper extremity of each of the coiled springs 2.0 is similarly connected to an upper spring holder bar assembly 30 by engaging one of the transverse pins 31. The holder bar assembly carries rollers 32 and 33 at each end to movably guide the assembly along the corresponding vertical frame support. Actually, the upper spring holder assembly 30 is disposed on one side of a spacer channel 34 within the vertical frame support, while the rail carriage is guided along the other side of the spacer channel and the rollers 32 and 33 are disposed in suitable spring guide channel tracks 36 and 37 respectively formed at each side of each vertical frame support, as best shown in the sectional view of Fig. 4 of the drawings.

The upper springholder assembly 30 includes a suitable bracket 35 and a connecting bar' assembly 40 which is normally disposed parallel to the springholder bar assembly 30. The bracket 35 may comprise two plates which are positioned outside the bar assemblies 30 and 40 respectively, and are connected thereto by pins 3 and 53 respectively. The plates may be connected together by pins 60 and 61. The extremities of the cables 22 and 23 are connected respectively to opposite ends of the connecting bar assembly 40 by means of suitable turnbuckle type connectors 41 and 42, while the other extremities of the cables extend upwardly through an opening 43 in the overhead frame cross member 19 and thence about the grooved cabled rum 24 which is keyed on a freely rotating shaft 21-. The shaft 21 is rotatably supported at each end on suitable pillow blocks 46 and 47, and a compensating cam 25 is keyed on each end of the shaft 21 on the opposite side of the corresponding pillow block from the cable drum. The cable drum 24 and compensating cam 25 at each end of the shaft 21 are spaced respectively from opposite sides of the corresponding pillow block by means of suitable bushings 50 and 51. The compensating cam 25 carries the cables 26 and 27 whose free extremities extend downwardly through another opening 45 in the cross member 19 to suitable turnbuckle connectors '48 and 49 for connection to the toggle link 28 on the corresponding rail carriage 15. It will be noted that the cable drum 24 and compensating cam 25 are mounted on each end of the shaft 21 so that the angle of inclination of the grooves are opposed to each other. Thus, as the cables 22 and 23 on the cable drum 24 are wound upwardly, the cables 26 and 27 on the compensating cam 25 are unwound to lower the tube head assembly 10. The compensating cam 25 co-acts with the cable drum 24 to continually offset the extension of the spring suspension and thereby maintain a uniform counterbalancing force for any selected position of the tube head assembly in the vertical plane of its travel. Thus, as the tube head is lowered and the spring suspension is extended, the reaction force within the springs is increased and it is necessary to increase the torque arm through which the tube head supporting cables 26 and 27 function in relation to the fixed torque of the cable drum. Similarly, as the tube head assembly is raised and the spring sus- 1 is anchored at the bottom to the lower spring holder bar injury to a patient lying underneath. Accordingly, as

best shown in Figs. 7 and 9 of the drawings, the connecting cable bar assembly 40 is pivotally connected by transverse pins 43 to the bracket plates 35 and carries an internal rectangular sleeve '55 which normally is loosely guided along a vertical latching bar 56. Preferably, the member 55 is welded to the bars 40. The bar 56 29 and serves as a stop member against which the sleeve 55 can frictionally engage when the bar assembly 40 is tilted about its pivot 53. Such frictional engagement operates to clamp the member 55 against the bar 56.

" This tilting action will occur if any one of the connecting {tinually compensated to provide effortless movement pension is retracted, the cable drum 24 releases its cables throughout the travel distance of the counterbalanced member and which includes a safety control feature in the form of a latching mechanism that automatically operates to immobilize the counterbalanced system in the event of a mechanical failure in the flexible connection between the spring suspension and the counterbalanced member, thereby increasing the protection to a patient as well as providing optimum operation throughout the range of movement.

We have shown and described what we consider to be the preferred embodiments of this invention, and it will be obvious to those skilled in the art that other changes may be made without departing from the scope of this invention as defined by the appended claims.

We claim:

1. In an X-ray apparatus having an X-ray tube mounted for movement along a vertical support, the combination comprising an overhead drum assembly rotatably mounted on the vertical support, a spring suspension having one end anchored to the base of the vertical support, at least a pair of flexible connecting members extending about said drum assembly and having one end connected to the X-ray tube, a second pair of flexible connecting members extending about said drum assembly and operatively connected to the spring suspension, latch means including a tiltable latch member having a central tilt axis secured to the other end of the spring suspension, and having its extremities on opposite sides of the tilt axis connected respectively to a different one of said second pair of flexible connecting members, and means on said tiltable latch member adapted frictionally to coact with the support to immobilize the X-ray tube against vertical movement downwardly consequent upon failure of any of said second set of flexible connecting members.

2. The apparatus of claim 1, wherein a vertical guide member is fixed to the support, and wherein the latch member has a central opening through which the vertical guide member extends, some of the walls of the opening being adapted to engage and clamp said latch member against the vertical guide member, consequent upon tilting movement of the latch member about its pivotal axis.

3. The apparatus of claim 1 wherein said drum assembly includes a drum having a cam surface formed to progressively offset the extension of the spring suspension to maintain a substantially uniform counterbalancing force throughout the extent of vertical movement of the X-ray tube head.

4. The apparatus of claim 1 wherein said drum assembly includes a cam surface of progressively increasing diameter for supporting the overrunning flexible connecting members, said cam surface being disposed axially in i 5 a manner to progressively offset the extension of the spring suspension and thereby maintain a substantially uniform counterbalancing force throughout the extent of vertical movement of the X-ray tube.

5. In an X-ray apparatus having an X-ray tube mounted for vertical movement along a vertical support the combination comprising, an overhead drum assembly including a drum of constant diameter and a drum of progressively increasing diameter each fixed coaxially on a common rotatable shaft with the smallest diameter end of the latter drum positioned adjacent the drum of constant diameter, a spring suspension having one end anchored to the base of the vertical support, a first set of flexible connecting members connecting the other end of the spring suspension to the constant diameter drum and adapted to be wound up thereon, and a second set of flexible connecting members connecting the X-ray tube to the large diameter end of the other dnum and adapted to be Wound up thereon, whereby the extension of said spring suspension is progressively offset to maintain a substantially uniform counterbalancing force throughout the extent of vertical movement of the X-ray tube.

6. In an X-nay apparatus having an X-ray tube mounted for movement along a vertical support the combination comprising, an overhead compound drum assembly in oluding a cylindrical portion of constant diameter and a cam portion of progressively decreasing diameter fixed for rotation on a common axis, a spring suspension hav ing one end anchored to the base of the vertical support, a set of flexible members interconnecting the other end of the spring suspension with the cylindrical portion of the drum and adapted to be Wound up thereon against the spring bias, a second set of flexible members interconnecting the X-ray tube with the large diameter end of the cam portion of the drum and adapted to be Wound up in the direction of decreasing diameter, said flexible members coacting on their respective drum portions to uniformly counterbalance the vertical movement of the X-ray tube along the vertical support.

References Cited in the file of this patent UNITED STATES PATENTS 1,043,833 Hinkel Nov. 12, 1912 1,470,698 Nelson Oct. 16, 1923 1,497,499 Girard June 10, 1924 2,168,209 Hanpt Aug. 1, 1939 2,291,114 Squyer July 28, 1942 2,471,998 Berggren May 31, 1949 2,506,228 Lofstrand May 2, 1950 2,678,788 Paulson May 18, 1954 

